McCarthyism, named after Joseph McCarthy, was a period of intense anti-communism, also known as a red scare, which occurred in the United States from 1948 to about 1956 (or later), when the government of the United States actively persecuted the Communist Party USA, its leadership, and others suspected of being communists. Loyalty tests were required for government and other employment and lists of subversive organizations were maintained.

The word "McCarthyism" is not a neutral term, but carries connotations of false, even hysterical, accusation. From the viewpoint of the political and cultural elite the suppression of radicalism and radical organizations in the United States was a struggle against a dangerous subversive element controlled by a foreign power that posed a real danger to the security of the country, thus justifying extreme, even extra-legal measures. From the radical viewpoint it can be seen as class warfare. From the viewpoint of the thousands of innocents who were caught up in the conflict it was a massive violation of civil rights.

One of the tools used was the McCarran Internal Security Act of 1950 which required Communists and Communist organizations to register with the federal government. The McCarran Act was gradually ruled unconstitutional in a series of Supreme Court decisions, beginning in 1964, and it was completely repealed in 1990. Another was the Smith Act of 1940, a federal criminal statute outlawing "advocacy of violent overthrow of the government."

Under the Smith Act, the leadership of the TrotskyistSocialist Workers Party were prosecuted, as was the leader of the Communist Party of the United States of America, Eugene Dennis, and eleven members of the party's National Committee. Since CPUSA had not explicitly advocated the violent overthrow of the U.S. government, the prosecution was on somewhat shaky ground, and based its case against the party's leaders on Communist works of literature they possessed. Instead of arguing this legal technicality, the CPUSA leadership denounced the law under which they were tried itself, a defence which failed. Others who were tried under the Smith Act in later years successfully based their defences on more technical grounds. The Smith Act was declared unconstitutional in its full form by the Supreme Court in 1957, and limited to much more specific offences.

Another major element of McCarthyism was the internal screening program on federal government employees, conducted by the FBI under J. Edgar Hoover. This comprehensive program vetted all federal government employees for Communist connections, and employed evidence provided by anonymous sources whom the subjects of investigation were not allowed to challenge or identify. From 1951, the program's required level of proof for dismissing a federal employee was for "reasonable doubt" to exist over their loyalty; previously it had required "reasonable grounds" for believing them to be disloyal.

The hearings conducted by Senator Joseph McCarthy gave the red scare the name which is in common usage, but the red scare predated McCarthy's meteoric rise to prominence in 1950 and continued after he was discredited by a Senate censure in 1954, following his disastrous investigation into the U.S. Army which started on April 22 of that year. McCarthy's name became associated with the phenomenon mainly through his prominence in the media; his outspoken and unpredictable nature made him ideal as the figurehead of anti-communism, although he was probably not its most important practitioner.

McCarthy headed the Permanent Investigating Subcommittee of the Senate Committee on Government Operations[?]; other significant legislative committees were the House Un-American Activities Committee (HUAC), officially called the United States House of Representatives' Committee on Un-American Activities, and the Senate equivalent, the Senate Internal Security Subcommittee[?]. These committees independently investigated and made allegations of communism against specific individuals. They had no official power of punishment, but those named as communists or communist sympathisers by the various committees often found themselves fired from their jobs and sometimes ostracised from society. These committees often received information on suspected communists and communist sympathisers from the FBI, which found them useful to attack suspects against which it did not have enough evidence to push for a criminal prosecution. These national committees were imitated by committees within state and even local government; these committees, sometimes known as 'little HUACs', were however generally less effective than the national committees.

The most publicly visible elements of McCarthyism were the trials of those accused of being communist agents within the government. The two most famous trials were those of Alger Hiss (who was not in fact convicted directly of espionage, but of perjury) and of Ethel and Julius Rosenberg. Such trials typically relied on information from informers, such as Whittaker Chambers (whose testimony led to the downfall of Hiss) and the three men whose confessions and testimony were vital to the Rosenberg trial, Klaus Fuchs, Harry Gold[?] and David Greengrass[?]. It was revealed in the 1990s that the government had been relying on access to secret Soviet communications that showed that all of these, Hiss, the Rosenbergs, Klaus Fuchs, and many others, including Harry Dexter White[?], U.S. Assistant Secretary of the Treasury, were in fact paid agents of the Soviet Union. These communications are known collectively as the Venona papers[?].

The Rosenbergs were convicted of conspiracy to commit espionage in 1951 and executed in 1953. Hiss was convicted in 1950 of perjury for denying on oath that he had passed documents to the Soviet Union while working for the State Department in the 1930s, and sentenced to ten years' imprisonment. Both cases have aroused considerable controversy down the years and remain debated in the present day, and have to some extent been revitalised by the opening of much of the Soviet archives in the early 1990s. This provided new evidence on all these cases, but the Venona evidence is still disputed by partisans.

The red scare affected many people in Hollywood, resulting in arrests of various figures in the film industry. Many were also "blacklisted", meaning that they were unable to work in the film industry (although some screenwriters were able to work under pseudonyms).

McCarthyism as a generic concept
Since the time of the red scare led by Joseph McCarthy, the term McCarthyism has entered the American vernacular as a general term for phenomenon of mass pressure, harassment, or blacklisting used to instill conformity with prevailing political beliefs. The Arthur Miller play "The Crucible", written during the McCarthy era, used the Salem witch trials as a metaphor for the McCarthyism of the 1950s, suggested that the underlying process of McCarthyism-style persecution can occur at any time and place.

Since the McCarthy era, fears of renewed forms of McCarthyism-style persecution have arisen. For example, in 2003, as intolerance arose against those in the film and television industry and elsewhere who opposed war with Iraq. Many were accused of being "anti-American" or "unpatriotic" for taking public stands on matters of conscience, or simply for stating views that were opposed to that of the government. Some, including reporter Peter Arnett[1] (http://abcnews.go.com/wire/Entertainment/ap20030331_548) and producer Ed Gernon[?][2] (http://www.cbsnews.com/stories/2003/04/11/entertainment/main548998.shtml), were denounced by their employers and lost their jobs.

The Screen Actors Guild issued a statement stating "We deplore the idea that those in the public eye should suffer professionally for having the courage to give voice to their views. Even a hint of the blacklist must never again be tolerated in this nation."